In addition to primary nutrients, such as carbon, hydrogen, oxygen, nitrogen, phosphorus and potash, plants require secondary nutrients and micronutrients. Secondary nutrients are required in quantities smaller than primary nutrients, and include calcium, sulfur and magnesium. Micronutrients are required in very small quantities, smaller than the quantities of secondary nutrients, and include zinc, manganese, iron, copper, molybdenum, boron, chlorine, cobalt and sodium.
The primary nutrients nitrogen phosphorus, and potash may be supplied through fertilizers. Depending on the needs of the plant, it is also possible to supply micronutrients through fertilizers. However, because of the very small quantities, it is difficult to incorporate the micronutrients into fertilizers in a manner that will deliver small amounts of the micronutrient(s) to each plant substantially uniformly.